Abstract
The 1H-NMR spectra of 8,9,10,11-tetrahydro-7H-cycloocta[de]naphthalene (1) and its 8,8,10,10-tetradeuterio derivative have been studied at various temperatures. The NMR parameters of compound 1 were determined accurately by means of computer analysis of the low-temperature spectrum. It was found that the ground-state conformation of 1 is a boat, which is somewhat in a distorted form (puckering) as a result of the steric repulsion between the interior benzyl protons. Activation parameters ΔG\eweq, ΔH\eweq, and ΔS\eweq for the boat inversion process in the molecule were obtained by the line-shape analysis method as 14.5, 16.1 kcal/mol and 5.4 e.u., respectively. These results are best explained in terms of a conformational interconversion process in which the pseudorotations of the peri bonds are involved. Some discussion is also made on the conformational properties of compound 1 in comparison with those of the structurally analogous benzocyclic compound 6,7,8,9-tetrahydro-5H-benzocycloheptene.
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